We are studying cone inputs to spatial detectors in human vision using the two-color increment threshold method of Stiles to isolate chromatic Pi-mechanisms. Some of the Pi-mechanisms have spectral sensitivities closely resembling the presumed spectral absorption functions for the various classes of human cones. The use of superimposed test targets or superimposed patterns, however, often show strong interactions of signals from various classes of cones. We are studying such interactions using both conventional spot test stimuli of Stiles and monochromatic, sinewave gratings generated directly on the retina as interference patterns of laser light. We are studying interactions of cone signals in short-wavelength pathways (Pi1 and Pi3) by studying how blue and yellow adapting fields interact antagonistically to control the saturated response of blue pathways. This method reveals very strong interactions using 1 deg test flashes, like Stiles's. We are also examining whether opponent-mechanisms control the adaptation of the short-wavelength pathways for all spatial frequency targets to which the pathways are sensitive. The mechanisms controlling the adaptive state of the middle (Pi4) and long-wavelength (Pi5) mechanisms are being examined with chromaticity mixed adapting fields and test patterns. Red and green adapting fields of high-intensity appear to act in a partially cancellative manner when the test patterns have strong components of low spatial and temporal frequency. For test patterns where either spectral or temporal frequency is high the fields appear to act additively, according to preliminary results. Detection of superimposed red and green test patterns on an intense yellow field does not follow the behavior which would be deduced from the assumption that Pi-mechanisms act as Unitary mechanisms. There is an enhanced snsitivity for chromaticity shifts. Again, detection is not governed by pathways controlled by single classes of cones.